Sciencemadness Discussion Board

Truvia Recrystallization (with interesting supersaturation)

Metacelsus - 13-10-2013 at 13:36

Today I wanted to recrystallize some Truvia (erythritol-based sweetener) to get the erythritol. I added 280 grams of Truvia, which says it contains 3 grams erythritol per 3.5 gram serving, or 86%, to 150 milliliters of distilled water, which I then heated until all dissolved (at 65 C) to form a clear, slightly yellow-tinged solution. I probably could have used less water, but I wanted to minimize the amount of impurities that precipitated. I then took the beaker containing the erythritol solution off the hotplate to cool and took the thermometer out. When I returned to it a few hours later, no crystals had formed. Intrigued, I put the thermometer back in to make sure that it had cooled to room temperature. When I did this, crystals of erythritol started to form around the thermometer, and very slowly spread to cover most of the flask (some liquid remained). I think the thermometer had some crystals of erythritol on it which served as seed crystals. What was remarkable how slowly the crystals spread. They took a good ten minutes to grow to their full extent. This might be a good companion to the classic sodium acetate "hot ice", if anyone can replicate it.

Update:
The yield was 250 g (89%) of recrystallized erythritol (pure white crystals). The leftover liquid was honey-colored. All in all, I am pleased with these results. I plan to use some of the purified erythritol to make ETN next weekend.

[Edited on 13-10-2013 by Cheddite Cheese]

PHILOU Zrealone - 14-10-2013 at 10:34

This is called "sursaturation" or "overfusion" effect.

Not only a remaining cristal seed on the thermometer can induce the rapid cristallization, but also scratches into the glass of the thermometer or of the beaker, vibrations, dusts or hair...

Such rapid "froozing" / cristallization will be less effective in excluding impurities from cristals than slow speed cristallization...

[Edited on 14-10-2013 by PHILOU Zrealone]

bfesser - 14-10-2013 at 10:36

supersaturation, freezing, crystallization, crystals

Please try an English-language spell checker, <strong>PHILOU Zrealone</strong>

Metacelsus - 14-10-2013 at 13:42

@PHILOU Zrealone

I wouldn't call the crystallization "rapid". I stared transfixed at the beaker for a good ten minutes. I am satisfied by the purity -- I measured a melting point of 112 C, and the product is completely colorless. Nonetheless, I think you are right in that crystallization the usual way would probably result in an even purer product. Also, smaller crystals might be easier do deal with than a huge mass, which I had to break up. Is there any easy way to prevent supersaturation (maybe using a scratched beaker)?

Poppy - 22-10-2013 at 16:18

Rapid crystalization is intendedly preferred over if a further was is to be practiced. So, if you find another solvent to perform the final crystalization or just wash away the water with the impurities, just tought that this should be good.

UnintentionalChaos - 22-10-2013 at 23:11

Not to distract from the original point of the thread, but pure erythritol is a consumer product in the US (Where OP is from). Looking in places that cater to "natural foods" type yuppies should find you a source. It runs something like $10/lb.

PHILOU Zrealone - 23-10-2013 at 12:51

Once you have crystals of the "pure material" from the first rapid crystallization; grind it into a fine dust and add it to the ambient T° near supersaturated solution of truvia.
Add under mixing the fine dust until no more dissolves.

The small dusts of erythritol will act as seeds for crystallization...the more seeding centers you will have, the more crystals of average smaller particle size you will have.
Place the recipient in the fridge

Metacelsus - 23-10-2013 at 13:29

I'm pretty satisfied with my results, so I don't think I'll do any more purification. I bought the Truvia on a whim, to see if I could satisfactorily purify it. I know that purer erythritol is easy to come by, but for me, Truvia is even easier to get. Once I distill some nitric acid, I will attempt to nitrate a small amount and see how it goes.

PHILOU Zrealone - 24-10-2013 at 12:25

Here in Belgium we have Stevia crystaline sweetener with erythritol as charge agent...
In Carrefour big departement store, 3,99€/300g ... it contains erythritol > 99%... the rest is stevioside what should be nitratable being a polyoside ;)

Metacelsus - 24-10-2013 at 13:00

Yes, Truvia is about the same thing. It is stevia with erythritol as a "bulking agent" i.e. filler. I hadn't though about nitrating the stevioside before. If the nitrated product is sufficiently stable, it might not even be necessary to purify the Truvia.

ScienceSquirrel - 24-10-2013 at 13:50

Any strong acid is going to mash up stevioside.
It will cleave those glucose units off and then mash them and the steviol structure up.
The honey coloured liquor reported by Cheddite Cheese probably contains these organic remains.
Extracting steviol glycosides from Truvia is probably a lot harder than extracting erythritol.
Extracting with cold ether and then concentrating the dried extracts in the cold might be the way to go.
The residue can then be crystallised to yield pure erythritol.

acid digest of stevioside

jwpa17 - 24-10-2013 at 15:03

"Any strong acid is going to mash up stevioside."
Exactly right - although it's a bit more robust than you might think. Stevioside has both glucose and sophorose sugars. Some Korean workers published an isolation of the sophorose from stevioside. At I recall, it took between 2 and 3 hours of boiling in 1 M HCl (may have that concentration wrong) to maximize the yield of sophorose.

Metacelsus - 27-11-2013 at 10:05

Update: I have successfully synthesized ETN from the recrystallized Truvia. I used 1.6 ml WFNA, 1.6 ml H2SO4, and 1 g erythritol. Since the ETN is not done drying, I do not have a precise yield yet.

Dany - 28-11-2013 at 01:09

@Cheddite Cheese

Since the Truvia is composed of 86% by weight, try to nitrate the Truvia, and finally try to recrystallized the crude product of nitration. Use a little excess of nitric acid/sulfuric acid for the nitration. If this work, it should be more practical than your procedure because you are purifing first the erythritol and than you are obliged to purify the erythritol tetranitrate (also by recrystallization). It is practical to perform the recrystallization once (for the final nitrated product).

Dany.

Metacelsus - 28-11-2013 at 13:03

My yield after recrystallization from ethanol was 1.68 grams. Before recrystallization I had 1.72 grams.

I think that purifying the erythritol before nitration is better than purifying ETN afterwards because then no acid is wasted nitrating things that aren't erythritol.


XeonTheMGPony - 14-1-2016 at 09:27

Quote: Originally posted by Cheddite Cheese  
My yield after recrystallization from ethanol was 1.68 grams. Before recrystallization I had 1.72 grams.

I think that purifying the erythritol before nitration is better than purifying ETN afterwards because then no acid is wasted nitrating things that aren't erythritol.




Some may be annoyed at me bouncing such an old thread, but I must say this was indeed my problem with poor yields!

By following this thread, I have gained a considerable improvement as noted here: http://www.sciencemadness.org/talk/viewthread.php?tid=7209&a... at page #03

Intergalactic_Captain - 8-2-2016 at 09:01

Just out of curiosity, have any of you had an issue with maltodextrin? I'm not going into any more detail for reasons of trade-secret bullshit, but lets just say that pretty much every truvia knockoff uses it as a bulking/flowing agent. We get our legit "truvia" straight from Cargill, so there's no BOM - Just a thought.